A gas turbine combustor is essentially a device used for mixing fuel and air, and burning the resulting mixture. Gas turbine compressors pressurize inlet air which is then turned in direction or reverse flowed to the combustor where it is used to cool the combustor and also to provide air to the combustion process. Multiple combustion chamber assemblies may be utilized to achieve reliable and efficient turbine operation. Each combustion chamber assembly comprises a cylindrical combustor liner, a fuel injection system, and a transition piece that guides the flow of the hot gas from the combustor liner to the inlet of the turbine section. Gas turbines for which the present fuel nozzle design is to be utilized may include one combustor or several combustors arranged in a circular array about the turbine rotor axis.
Traditional gas turbine combustors use diffusion (i.e., non-premixed) combustion in which fuel and air enter the combustion flame zone separately and mix as they burn. The process of mixing and burning produces flame temperatures exceeding 3900° F. Because diatomic nitrogen rapidly disassociates and oxidizes at temperatures exceeding about 3000° F. (about 1650° C.), the high temperatures of diffusion combustion result in relatively high NOx emissions.
The ability to control the amount of fuel flow to different regions of the combustor allows for the minimizing of CO and NOx emissions for a given set of operating conditions.
Accordingly, there is a need for independent variable control of fuel flow to fuel introduction locations of the combustor as a means to further reduce emissions across full ambient ranges and gas turbine load ranges and provide an additional tuning level for enhanced operability optimization.